The present invention relates to a phosphor for white light emitting diode and a light emitting device using the same as a light source.
Recently, there are two methods to manufacture and a white LED using a fluorescent material and a GaN or InGaN chip.
The methods use a single chip and coat a fluorescent material on a blue LED chip or a near-ultraviolet (NUV) LED chip to obtain white light. In particular, the methods use blue light released from a blue LED and yellow light obtained by exciting Y3Al5O12:Ce3+ (YAG:Ce) using some of the blue light, by applying a fluorescent material to one chip, to release a white color.
Like this, a white LED uses a fluorescent material, which converts a blue LED and blue light released from the blue LED into a yellow color, or a fluorescent material, which converts a near-ultraviolet LED and the near-ultraviolet into blue, green and red colors, to realize a white LED. Therefore, a fluorescent material for an LED used in a white LED device is a ceramic powder material converting light released from an LED into visible light (namely, red, yellow, green, and blue light) and is an essential material to realize white light. That is, light emitting efficiency of phosphors is one variable related to white light emission when applied to a light emitting diode.
Meanwhile, presently used garnet-based phosphors have advantages such as high fluorescence efficiency and broad applicability, but does not autonomously emit blue light and has drawbacks such as lack of fluorescence in a red wavelength area. Therefore, when white light emitting diode is realized using the light source, white light in a cool white light area is released by low red light emitting characteristics and narrow blue excitation light and, as such, white light having a low color rendering index and high color temperature is realized.
In addition, U.S. Pat. Nos. 8,088,304 and 0,279,022 disclose technologies with respect to a garnet-based phosphor using cerium as an activator. The technologies tried to improve light characteristics by adding a small amount of thorium. However, the inventions used cerium as a main activator and thereby a light emitting wavelength range of garnet-based phosphors is limited and the above problems are still present.